Over in The Atlantic, there's a great quick-and-dirty history of the science fiction book cover, courtesy of the folks at SF bookstore Singularity & Co. Starting with the pulpy artwork of artists like Frank R. Paul and others, the covers progressed into some fairly cartoony images of aliens and rocketships in the 1950s, before embracing abstraction and pop art in the 1960s... and then slowly returning to the cartoony and pulpy images the genre had started to abandon. The whole thing is well worth reading. [The Atlantic]